Generally, Mobile Network Operators want the mobile telecommunication terminal such as a cell phone and a personal digital assistant (PAD) with high ability to transmit and receive the signal, to ensure the quality of the signal transmitting and receiving. For example, many Mobile Network Operators measure and evaluate the signal transmitting signal and receiving ability of the cell phone using total radiated power (TRP) and total radiation sensitivity (TIS), in which TRP is used to evaluate the signal transmitting ability, and TIS is used to evaluate the signal receiving ability. The larger TRP of cell phones is, the larger the total radiation of the cell phone. Mobile Network Operators usually hope that the mobile telecommunication terminal has a large TRP, and a strong ability to transmit signals.
However, considering user's safety, it is hoped to reduce the harmful electromagnetic radiation of the cell phone to the user. When a user uses a cell phone, the cell phone is near the head of the user, particularly, the receiver is near the ear of the user. Radio waves transmitted from the cell phone to base station are more or less absorbed by the user, so that the health of the user may be hurt due to changing of the user's body tissue by the radio wave. In many countries, the radiation of the cell phone to the user must be less than the stipulated standards such as cell phone radiation absorption rate SAR (Specific Absorption Rate) Measurements. In North America and Europe, SAR testing is a mandatory standard, and the cell phone that does not satisfy the standard can not be sold in the market.
Hearing aid compatible (HAC) is another new measurement standard related to electromagnetic radiation of the cell phone. Because the cell phone may interfere with the a hearing aid, the user wearing the hearing aid may heard noise he should not hear, thus influencing the quality of the signal receiving. For the user wearing the hearing aid to use cell phone normally and ensuring the hearing impaired people to enjoy the same rights, HAC standards require the cell phone to operate with the hearing aid compatibly, and provide the measure methods and limit standard.
Cell phones are needed to have a strong signal transmitting ability (TRP meets the standard of the network operators), to have a low of radiation to users (SAR value is small), and to meet the requirements of HAC.
However, the conventional mobile telecommunication terminal such as cell phones can, not meet the standards and requirements without professional design.